Today the US Patent & Trademark Office published a patent application from Apple that relates to audio loudspeakers and in particular, but not exclusively, to a coating that could improve iPhone and iPad Pro loudspeaker sound quality and to audio loudspeakers that use the coating in their back volumes to improve loudspeaker performance.

In Apple's patent background they note that loudspeakers typically include a back volume and a membrane or diaphragm that oscillates and emits sound when driven by an electromagnetic transducer. A variety of different forces act on the membrane while it is being moved, distorting its intended acceleration by the electromagnet and thus distorting the sound waves it emits. Reduction of these additional membrane forces leads to improved sound quality.

One of the forces acting on the membrane results from pressure fluctuations in the back volume due to compression and decompression by the moving membrane of air in the back volume. These pressure fluctuations can be reduced by increasing the space of the back volume--e.g., by making it larger. But in hand-held devices such as cell phones, increasing the size of the back volume is possible only to a minor degree because these devices should be kept conveniently small.

Apple's invention covers various aspects of an audio speaker and in particular, but not exclusively, to a coating that improves loudspeaker sound quality and to audio loudspeakers that use the coating in their back volumes to improve loudspeaker performance.

The audio speaker includes a housing defining a back volume behind a speaker driver, so that the speaker driver can convert an electrical audio signal into a sound and the sound can propagate through a gas in the back volume. A highly porous acoustically active coating is deposited on at least one interior surface of the back volume, the highly porous coating including a binder and an adsorptive substance.

Aspects are described of an acoustically active coating. In one aspect the coating is a highly porous coating having a thickness and including between 2% and 30% by mass of a binder and between 70% and 98% by mass of a zeolite.

The coating comprises an irregular matrix formed by a plurality of convex shapes connected by concave connectors and has a distribution of pore sizes. Other embodiments are disclosed and claimed.

Aspects are described of a process including preparing a slurry including a binder and a zeolite. The slurry is sprayed through a nozzle having a nozzle diameter. A highly porous acoustically active coating is deposited on a substrate by directing the sprayed slurry through an environment onto the substrate, the substrate being positioned at a distance from the nozzle.

Apple's patent FIG. 2A below illustrates various aspects of an iPhone's audio speaker; FIG. 5 illustrates an aspect of a sprayer system #500 for forming an acoustically active coating.

Apple's patent FIG. 6 below is a flowchart of an aspect of a process for forming an acoustically active coating on a wall of a loudspeaker back volume as shown in FIG. 5 above; FIG. 7 is a scanning electron microscope (SEM) photograph of an aspect of a coating.

To dig deeper into the details of this invention, review Apple's patent application number  20210144465.

For the record, LinkedIn doesn't have any information on the two engineers listed on this patent that are from Germany. These engineers were also listed on another Apple patent regarding audio that was granted back in 2020 titled "Acoustic filler including acoustically active beads and expandable filler." Whether Apple acquired these patents is unknown at this time.

Considering that this is a patent application, the timing of such a product to market is unknown at this time.